function test(){
    var drag = new Drag('box2');
    drag.init();
}
function Drag(id){
    this.obj = document.getElementById(id);
    this.disx;
    this.disy;
}
Drag.prototype.init = function(){
    var me = this;
    this.obj.onmousedown = function(e){
        var e = e || event;
        me.mouseDown(e);
        return false;
    };
};
Drag.prototype.mouseDown = function(e){
    var me =this;
    this.disx = e.clientX - this.obj.offsetLeft;
    this.disy = e.clientY - this.obj.offsetTop;
    document.onmousemove = function(e){
        var e = e || event;
        me.mouseMove(e);
    };
    document.onmouseup = function(e){
        var e =e || event;
        me.mouseup(e);
    }
};
Drag.prototype.mouseMove = function(e){
    this.obj.style.marginLeft = (e.clientX - this.disx) + 'px';
    this.obj.style.marginTop = (e.clientY - this.disy) + 'px';
};
Drag.prototype.mouseup =function(e){
    document.onmousedown = null;
    document.onmousemove =null;
    document.onmouseup = null;
    return false;
};
test();
console.log("ppp");